Tyrosyl phosphorylation regulates human cellular processes from cell differentiation and growth to apoptosis. The process of tyrosyl phosphorylation is regulated by protein-tyrosine phosphatases (PTP) and protein-tyrosine kinases (PTK). When this regulation is disrupted, diseases such as cancer can arise. (Mohi and Neel, The role of Shp2 (PTPN11) in cancer. Curr Opin Genet & Dev. 2007, 17, 23-30). Many studies in the last three decades have demonstrated the roles of various protein tyrosine kinases (PTKs) in human cancer (Blume-Jensen and Hunter, Oncogenic kinase signalling. Nature 2001; 411:355-65). PTK inhibitors such as imatinib and gefitinib are now well-recognized as targeted therapy drugs in cancer treatment (Deininger, et al., The development of imatinib as a therapeutic agent for chronic myeloid leukemia. Blood 2005; 105:2640-53; Mulloy, et al., Epidermal growth factor receptor mutants from human lung cancers exhibit enhanced catalytic activity and increased sensitivity to gefitinib. Cancer Res 2007; 67:2325-30). Though more research exists for PTKs, as the first PTK was synthesized 10 years earlier than the first PTP, recent discoveries have found that PTPs have a prominent role in tyrosyl phosphorylation. (Alonso, et al., Protein tyrosine phophatases in the human genome. Cell. 2004, 117, 699-711).
PTPs catalyze the reverse reaction of PTKs, however increasing evidence suggests that cell signaling and oncogenesis require coordinated action of both PTKs and PTPs. For instance, PTPs such as Shp2, PTP1B, Cdc25, and PRL-3 have been found to be positively involved in oncogenesis and tumor progression (Bentires-Alj, et al., Activating mutations of the noonan syndrome-associated SHP2/PTPN11 gene in human solid tumors and adult acute myelogenous leukemia. Cancer Res 2004; 64:8816-20; Boutros, et al., CDC25 phosphatases in cancer cells: key players? Good targets? Nat Rev Cancer 2007; 7:495-507; Stephens B J, Han H, Gokhale V, Von Hoff D D. PRL phosphatases as potential molecular targets in cancer. Mol Cancer Ther 2005; 4:1653-61; Tonks and Muthuswamy, A brake becomes an accelerator: PTP1B-a new therapeutic target for breast cancer. Cancer Cell 2007; 11:214-6). Consequently, the search for PTP inhibitors as a new class of potential drugs for targeted cancer therapy has intensified in recent years (Jiang and Zhang, Targeting PTPs with small molecule inhibitors in cancer treatment. Cancer Metastasis Rev 2008; 27:263-72; Lawrence, et al., Inhibitors of Src homology-2 domain containing protein tyrosine phosphatase-2 (Shp2) based on oxindole scaffolds. J Med Chem 2008; 51:4948-56; Hellmuth, et al., Specific inhibitors of the protein tyrosine phosphatase Shp2 identified by high-throughput docking. Proc Natl Acad Sci USA 2008; 105:7275-80; Geronikaki, et al. 2-Thiazolylimino/heteroarylimino-5-arylidene-4-thiazolidinones as new agents with SHP-2 inhibitory action. J Med Chem 2008; 51:5221-8; Johnston, et al., Cdc25B dualspecificity phosphatase inhibitors identified in a high-throughput screen of the NIH compound library. Assay Drug Dev Technol 2009; 7:250-65).
Shp2, encoded by the PTPN11 gene, is a non-receptor PTP containing two SH2 domains, a PTP domain, and a C-terminal region (Neel, et al., The ‘Shp’ing news: SH2 domain-containing tyrosine phosphatases in cell signaling. Trends Biochem Sci 2003; 28:284-93). It is part of the src homology domain (SH2) and necessary for embryonic development and growth factor, cytokine, and extra-cellular matrix signaling (Salmond and Alexander, SHP2 forecast for the immune system:fog gradually clearing. Trends Immunol 2006, 27, 154-60) and effect cell proliferation, differentiation, and migration. The N-SH2 domain in the wildtype Shp2 interacts with the PTP domain, resulting in autoinhibition of the Shp2 PTP activity. When the SH2 domains bind to specific phosphotyrosine docking sites in growth factor- or cytokine-stimulated cells, it relieves the autoinhibition and Shp2 is activated (Cunnick, et al., Phosphotyrosines 627 and 659 of Gab1 constitute a bisphosphoryl tyrosine-based activation motif (BTAM) conferring binding and activation of SHP2. J Biol Chem 2001; 276:24380-7).
A well-recognized Shp2-regulated signaling pathway is the Ras-Erk1/2 MAP pathway. For instance, Shp2 is positively involved in epidermal growth factor (EGF)-stimulated Erk1/2 activation (Cunnick, et al., Phosphotyrosines 627 and 659 of Gab1 constitute a bisphosphoryl tyrosine-based activation motif (BTAM) conferring inding and activation of SHP2. J Biol Chem 2001; 276:24380-7; Ren, et al., Roles of Gab1 and SHP2 in paxillin tyrosine dephosphorylation and Src activation in response to epidermal growth factor. J Biol Chem 2004; 279:8497-505). Shp2 PTP activity is required for transformation of human glioblastoma cells by EGFRvIII (Zhan, et al., The protein tyrosine phosphatase SHP-2 is required for EGFRvIII oncogenic transformation in human glioblastoma cells. Exp Cell Res 2009; 315:2343-57) and human mammary epithelial cells by ErbB2 (Zhou and Agazie, Molecular mechanism for SHP2 in promoting HER2-induced signaling and transformation. J Biol Chem 2009; 284:12226-34). In the last few years, mutations in the Shp2 gene PTPN11 have been identified in several types of leukemias and in some cases of solid tumors (Bentires-Alj, et al. Activating mutations of the noonan syndrome-associated SHP2/PTPN11 gene in human solid tumors and adult acute myelogenous leukemia. Cancer Res 2004; 64:8816-20; Tartaglia and Gelb, Germ-line and somatic PTPN11 mutations in human disease. Eur J Med Genet 2005; 48:81-96; Mohi and Neel, The role of Shp2 (PTPN11) in cancer. Curr Opin Genet & Dev. 2007, 17, 23-30).
Mutations in the PTPN11 gene and Shp2 can cause Noonan syndrome, juvenile myelomonocytic leukemia, acute myelogenous leukemia, and LEOPARD (lentigines, electrocardiogram abnormalities, ocular hypertelorism, pulmonic valvular stenosis, abnormalities of genitalia, retardation of growth, and deafness). Within these diseases, Shp2 is uninhibited and interacts with the docking protein Gab family. This interaction activates a pathway leading to cell proliferation and tumorigenesis. The identification of Shp2's role in these diseases is very important for developing cancer therapy. Targeting and inhibiting Shp2 with small molecule inhibitors has become a major goal in developing a new cancer therapy. These mutations and other cancer-associated Shp2 mutants are predicted or have been demonstrated to be gain-of-function mutations (Bentires-Alj, et al. Activating mutations of the noonan syndrome-associated SHP2/PTPN11 gene in human solid tumors and adult acute myelogenous leukemia. Cancer Res 2004; 64:8816-20; Ren, et al., Shp2E76K mutant confers cytokine-independent survival of TF-1 myeloid cells by up-regulating Bcl-XL. J Biol Chem 2007; 282:36463-73; Keilhack, et al., Diverse biochemical properties of Shp2 mutants. Implications for disease phenotypes. J Biol Chem 2005; 280:30984-93). Importantly, no loss-of-function Shp2 mutant has ever been found in human cancer.
Shp2 plays a positive role in the Ras-Erk1/2 MAP kinase pathway, however several reports indicated that Shp2 is a negative regulator of interferon (IFN) signaling. Shp2 was able to dephosphorylate STAT1 in vitro, suggesting that STAT1 is a substrate of Shp2 PTP (Wu, et al., SHP-2 is a dualspecificity phosphatase involved in Stat1 dephosphorylation at both tyrosine and serine residues in nuclei. J Biol Chem 2002; 277:47572-80). Consistently, increased IFN-stimulated STAT1 tyrosine phosphorylation was observed in mouse embryonic fibroblast cells lacking a functional Shp2 (Wu, et al., SHP-2 is a dualspecificity phosphatase involved in Stat1 dephosphorylation at both tyrosine and serine residues in nuclei. J Biol Chem 2002; 277:47572-80; You, et al., Shp-2 tyrosine phosphatase functions as a negative regulator of the interferon-stimulated Jak/STAT pathway. Mol Cell Biol 1999; 19:2416-24). The inhibitory effect of Shp2 on STAT1 tyrosine phosphorylation may contribute to modulation of the antiviral effect of IFN (Baron and Davignon, Inhibition of IFN-gamma-induced STAT1 tyrosine phosphorylation by human CMV is mediated by SHP2. J Immunol 2008; 181:5530-6).
While PTPs have increasingly attracted attention as novel targets of cancer drug discovery, only a few selective PTP inhibitors have been characterized biologically. Among PTP inhibitors identified in recent years, many of them contain one or more negatively-charged functional groups (Jiang and Zhang, Targeting PTPs with small molecule inhibitors in cancer treatment. Cancer Metastasis Rev 2008; 27:263-72; Hellmuth, et al., Specific inhibitors of the protein tyrosine phosphatase Shp2 identified by high-throughput docking. Proc Natl Acad Sci USA 2008; 105:7275-80; Bialy and Waldmann, Inhibitors of protein tyrosine phosphatases: next-generation drugs? Angew Chem Int Ed Engl 2005; 44:3814-39; Chen, et al., Discovery of a novel shp2 protein tyrosine phosphatase inhibitor. Mol Pharmacol 2006; 70:562-70). This property is reminiscent of PTP substrates since phosphotyrosine is negatively charged and negatively charged Asp and Glu residues are frequently present near tyrosine phosphorylation sites. While aryl sulfonic compounds have been found to exert cellular activities in some cases (Hellmuth, et al., Specific inhibitors of the protein tyrosine phosphatase Shp2 identified by high-throughput docking. Proc Natl Acad Sci USA 2008; 105:7275-80; Zhan, et al. The protein tyrosine phosphatase SHP-2 is required for EGFRvIII oncogenic transformation in human glioblastoma cells. Exp Cell Res 2009; 315:2343-57; Chen, et al., Discovery of a novel shp2 protein tyrosine phosphatase inhibitor. Mol Pharmacol 2006; 70:562-70; Zhao, et al., Regulation of ACh receptor clustering by the tyrosine phosphatase Shp2. Dev Neurobiol 2007; 67:1789-801; Fuchikawa, et al. Protein tyrosine phosphatase SHP2 is involved in Semaphorin 4D-induced axon repulsion. Biochem Biophys Res Commun 2009; 385:6-10), compounds containing aryl phosphate or carboxylate groups often require modifications for cell permeation and/or prodrug strategies for delivery into cells (Boutselis, e tal. Synthesis and cell-based activity of a potent and selective protein tyrosine phosphatase 1B inhibitor prodrug. J Med Chem 2007; 50:856-64).
Currently, there are a few known inhibitors of Shp2. Two of these compounds are CDL 4340-0580 and NAT6-297775, seen in FIG. 1. (Noren-Muller A., et al.: Discovery of protein phosphatase inhibitor classes by biology-oriented synthesis. Proc Natl Acad Sci USA. 2006, 103, 10606-11). Although these compounds have the ability to inhibit Shp2, they also inhibit tumor suppressor Shp1, which is not the cause of these malignancies. Ultimately, a Shp2 inhibitor should only affect Shp2 and not other important cellular processes.
Accordingly, there remains an unmet need for additional inhibitory compounds for the prevention and treatment of precancerous or cancerous lesions, particularly for lesions utilizing Shp2. The present invention further meets these important needs, and others, as will become apparent in the teachings that follow.